NAME

       Xray::Scattering::CromerMann - Perl interface to Thomspon scattering factors

SYNOPSIS

         use Xray::Scattering;
         Xray::Scattering->load('CroMann');
         $fnot = Xray::Scattering->get_f($symb, $d);

DESCRIPTION

       This module provides a functional interface to the Cromer-Mann table of coefficients for calculating the
       Thomson (kinematical) scattering factors of the elements and common valence states.  The coefficients are
       stored externally in the cromann.db database file.  The coefficients are for an Aikman expansion, which
       is of this form:

                 4
           f0 = sum [ ai*exp(-bi*s^2) ] + c
                i=1

       Thus there are 9 coefficients for each of the 213 tabulated element/valence symbols.

       "s" is "sin(theta)/lambda".  "(lambda*s)/2pi" is the momentum transfer.  "s" is simply related to the
       crystal d-spacing by "s=1/2d".

       The data for these tables can be found in Volume C of the International Tables of Crystallography, ed.
       A.J.C. Wilson, published by IUCr and Kluwer Academic Publishers (1992).  The table starts on page 500 and
       a discussion can be found on page 487.

       These tables are known to be inaccurate, particularly at high angles.  This module is a toy.  It is
       suitable for a student or for the sort of quick-n-dirty crystallographic hackery that the author indulges
       in.

CLASS METHODS

       "get_f"
           This  function  calculates  the  Thomson  scattering  for  a given symbol and d-spacing.  The Thomson
           scattering depends only on the momentum transfer.  The  d-spacing  of  the  scattering  planes  is  a
           closely related quantity and is easily calculated from the crystal structure, see Xtal.pm.

             $symb = "Ce3+";
             $fnot = Xray::Scattering->get_f($symb, $d);

           If  the  symbol  cannot  be  found  in  the table, "get_f" returns 0.  It also returns 0 when $symbol
           consists of whitespace or is "null" or "nu".  If $symbol is a number or the name of an element,  then
           it assumes you want the Thomson scattering for the neutral element.  The absolute value of $d_spacing
           is used by this function.

           If  you  ask for a valence state that is not in the table but for an element whose 0+ state is in the
           table, this method returns the scattering factor for the 0 valent atom.

       "get_coefficients"
           This returns the 9 element list containing the coefficients for the given symbol.

              @coefs = Xray::Scattering->get_coefficients($elem)

           Returns the array a1,b1,a2,b2,a3,b3,a4,b4,c.

           If you ask for a valence state that is not in the table but for an element whose 0+ state is  in  the
           table, this method returns the coefficients for the 0 valent atom.

       "has"
           This  is  a  test  of  whether  a given symbol is tabulated in the Cromer-Mann table.  It returns the
           symbol itself if found in the table or 0 if it is not in the table.

             $symb = "Ce3+";
             $is_tabulated = Xray::Scattering->has($symb);

ELEMENTS AND VALENCE STATES

       The following is a list of symbols for the tabulated elements and valence states.  The final two are ways
       of refering to an empty site (i.e. a null or blank atom).

             H      H.     H1-    He     Li     Li1+   Be
             Be2+   B      C      C.     N      O      O1-
             F      F1-    Ne     Na     Na1+   Mg     Mg2+
             Al     Al3+   Si     Si.    Si4+   S      P
             Cl     Cl1-   Ar     K      K1+    Ca     Ca2+
             Sc     Sc3+   Ti     Ti2+   Ti3+   Ti4+   V
             V2+    V3+    V5+    Cr     Cr2+   Cr3+   Mn
             Mn2+   Mn3+   Mn4+   Fe     Fe2+   Fe3+   Co
             Co2+   Co3+   Ni     Ni2+   Ni3+   Cu     Cu1+
             Cu2+   Zn     Zn2+   Ga     Ga3+   Ge     Ge4+
             As     Se     Br     Br1-   Kr     Rb     Rb1+
             Sr     Sr2+   Y      Y3+    Zr     Zr4+   Nb
             Nb3+   Nb5+   Mo     Mo3+   Mo5+   Mo6+   Tc
             Ru     Ru3+   Ru4+   Rh     Rh3+   Rh4+   Pd
             Pd2+   Pd4+   Ag     Ag1+   Ag2+   Cd     Cd2+
             In     In3+   Sn     Sn2+   Sn4+   Sb     Sb3+
             Sb5+   Te     I      I1-    Xe     Cs     Cs1+
             Ba     Ba2+   La     La3+   Ce     Ce3+   Ce4+
             Pr     Pr3+   Pr4+   Nd     Nd3+   Pm     Pm3+
             Sm     Sm3+   Eu     Eu2+   Eu3+   Gd     Gd3+
             Tb     Tb3+   Dy     Dy3+   Ho     Ho3+   Er
             Er3+   Tm     Tm3+   Yb     Yb2+   Yb3+   Lu
             Lu3+   Hf     Hf4+   Ta     Ta5+   W      W6+
             Re     Os     Os4+   Ir     Ir3+   Ir4+   Pt
             Pt2+   Pt4+   Au     Au1+   Au3+   Hg     Hg1+
             Hg2+   Tl     Tl1+   Tl3+   Pb     Pb2+   Pb4+
             Bi     Bi3+   Bi5+   Po     At     Rn     Fr
             Ra     Ra2+   Ac     Ac3+   Th     Th4+   Pa
             U      U3+    U4+    U6+    Np     Np3+   Np4+
             Np6+   Pu     Pu3+   Pu4+   Pu6+   Am     Cm
             Bk     Cf     O2-.   ' '    Nu

AUTHOR

         Bruce Ravel, bravel AT bnl DOT gov
         http://cars9.uchicago.edu/~ravel/software/exafs/

perl v5.34.0                                       2022-06-28                  Xray::Scattering::CromerMann(3pm)